The present disclosure relates to electric double layer capacitors (EDLCs) that include an alkylating or arylating agent additive capable of scavenging nucleophilic species generated during operation of the EDLC. Capacitors are typically used as components of electric circuits that are capable of holding an electric charge electrostatically, and discharging it rapidly. EDLCs, also known as supercapacitors or ultracapacitors, are a type of capacitor that have two electrodes separated by an ion permeable membrane (separator), and an electrolyte solution electrically connecting both electrodes.
Although EDLCs typically have lower energy densities than traditional batteries, they often can have much higher power densities. For instance, some EDLCs can have power densities up to 100 times higher than traditional batteries. This allows them to be used for many commercial applications such as, electric and hybrid automobiles.
One drawback of current EDLCs is that nucleophilic species can be generated in the electrolyte solution as a consequence of the normal functioning of the cell. For instance, trace hydroxide ion derived from adventitious water within an EDLC electrolyte solution may react with tetraethylammonium chloride to produce triethylamine via a Hoffman elimination type-mechanism. The triethylamine, or other nucleophilic species thus generated, can then further react within the cell and impede the EDLC's normal function.